Approach control apparatus for railway signaling systems



Mag'ch 10,1942. H. e. BLOSSER "'APPRoAcH coumoL APPAaA'Tiis FOR RAILWAY SIGNALING SYSTEMS 2 Sheets-Sheet 1 Original Filed July 29, 1938 H15 ATTORNEY March 10, 1942'.

H. G. B LOSSER APPROACH CONTROL APPARATUS FOR RAILWAY SIGNALING SYSTEMS Original Filed July 29, 1938 2 Sheets-Sheet 2 w mg INVENTOR Herm fllossen HLS A'IZTORNEY 'quickens its response to the Patented Mar. 10, 1942 APPROACH CONTROL APPARATUS FOR RAILWAY SIGNALING SYSTEMS Herman G. Blosser,

The Union Switch Pittsburgh, Pa., assignor to & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Original application Jul 222,014. Divided and 1939, Serial No. 285,568

6 Claims.

My invention relates to approach control apparatus for use in railway signaling systems of the coded track circuit class and it has special reference to the employment of such apparatus for approach controlling various signaling functions without the use of line wires.

This application is a division of an earlier application Serial No. 222,014 filed by me on July 29, 1938, for Approach control apparatus for railway signaling systems and now identified as Reissue Patent No. 21,783 dated April 29, 1941, and assigned to The Union Switch and Signal Company. As in that earlier case, the broad object of the present invention is to improve certain features of an approach control without line wire scheme wherein the rails of each unoccupied signal block length of track transmit code step pulses of auxiliary energy forwardly from the block entranceto efiect the energization of a slow release approach relay at the block exit.

A more specific object is to supply the referred to pulses of auxiliary energy to the entrance end of each track circuit in an improved manner which does not interfere with the normal code following operation of the associated signaling system track relay and which eliminates wastage of power at the location of that relay.

Another object is to receive these pulses at the exit end of the track circuit and to energize the associated slow release approach relay in step with them in a novel manner which reduces the necessary delay period of that relay and thereby entry of a train into the signal block.

An additional object is to provide for a double functioning of the contacts of the track circuit coding devices in their control of the combined signaling and approach governing equipment which is installed at the exit end of each signal block.

A still further'obg ect is to provide cut section facilities which are suitable for use with approach control schemes which embody my improved features.

' In practicing my invention I attain the above and other objects and advantages by transferring the entrance end connection of the track circuit from the signaling system track relay to a source of auxiliary energy at the beginning of each off code period and returning it to the track relay before the beginning of the next on period; by providing the exit end of each track circuit with a code following detector relay which is operated by auxiliary energy received from the y 29, 1938; Serial No. this application July 20,

rails, which is equipped with a supplemental stick circuit and other special release delaying means, and which locally controls the energization of the associated slow release approach relay; and by carrying the pick-up and the stick circuits of the detector relay through separate contacts of the signaling system coding device and so arranging these two contacts that they act in parallel in making and breaking the circuit over which the rails receive coded signal control energy.

I shall describe a few forms of approach control apparatus embodying my invention and shall thenpoint out the novel features thereof in claims. These illustrative embodiments are disclosed in theaccompanying drawings in which: Fig. 1 is a diagrammatic representation of a single section of railway track which is equipped with one preferred form of my improved non line wire approach control equipment;

Fig. 2 is a diagrammatic view of out section facilities which are suitable for use with the approach control scheme of Fig. 1;

Fig. 3 is a similar representation of exit end facilities which include provision for a double functioning of the contacts of the signaling system coding device;

Fig. 4 is a diagrammatic showing of a signal location equipment in which my improved approach control apparatus is combined with signaling system decoding apparatus of representative character; and

Figs. 5 and 6 are similar views of further forms of cut section facilities which are suitable for use with the approach control schemes disclosed herein.

. In the several views of the drawings, like reference characters designate corresponding parts. Referring first to Fig. l, the improved approach control apparatus of my invention is there disclosed in association with a coded track circuit system of automatic block signaling for a railway track l-2 over which it will be assumed that traific moves in the single direction indicated by the arrow, or from left to right in the diagram. The protected stretch of this track is divided into the customary successive sections by insulated rail joints 3 and the rails of each section form a part of a track circuit to which coded signal control energy is supplied in customary manner.

-In this view of Fig. 1, reference characters D and E respectively designate the entrance and the exit ends of one of these track sections which is illustratively shown as being a full signal block in length; character TR designates a code following track relay which is installed at the entrance end of the section and operated by energy received from the rails thereof; character TB 2. track battery or other direct current source provided at the section exit for the purpose of supplying these rails with the relay operating energy just referred to; character CR a coding device having a contact 5 which codes this energy by periodically interrupting the rail supply circuit; and character S the usual wayside signal which guards the entrance of each of the track blocks and which is controlled by the associated track relay TR through the medium of decoding apparatus An automatic block signaling system of the referred to coded track circuit type operates without the aid of line wires and in representative form it includes all of the elements above named. Such a system further comprises the customary facilities (not shown in Fig. 1) for continuously operating each of the exit end relays CR at one or another of the usual plurality of distinctive code rates. Selection among these rates (which in a typical three indication system may consist of '7 5 and 180 energy pulses per minute) is made in accordance with advance trafific conditions by the decoding apparatus In functioning in customary manner.

This decoding apparatus (details not shown in Fig. 1) is controlled in the usual fashion by the associated track relay TR and it performs the further function of selectively setting up a lighting circuit for one or another of the lamps (G, Y and R in the typical three indication system above referred to) of the wayside signal S at the same location. In the arrangement represented these signal lamps derive energizing current from a power source which is designated by the terminals plus and minus.

For applications in which train carried cab signals (not shown) also are to be controlled, the representative coded signaling facilities may still further comprise means at the exit end of the track circuit for additionally supplying the rails thereof with coded alternating current energy. In the form shown at location E in Fig. 1, such means include a tuned alternator TA which at proper times introduces alternating current energy of 100 cycle per second or other suitable carrier wave frequency into the rail supply circuit which coding contact 5 of device TR completes during each energy on period of the direct current signal control code from battery TB.

In order that certain functions of the signaling system may be rendered active only upon the approach of a train, the apparatus installed at each of the signal locations D, E, etc. is supplemented by an approach relay AR which is arranged to maintain the referred to functions inactive at all times except when the section of track to the rear of the location becomes occupied. In the illustrative arrangement which is shown at location E in Fig. 1, these approach controlled functions consist in lighting the wayside signal Se (normally dark) and in supplying the rails of the track section to the rear of that signal with coded alternating current energy for cab signal control.

The former function is governed by a contact 9 of the approach relay AR and the latter by a companion contact H thereof. Either of these functions may, of course, be controlled individually by the approach relay and it will be apparent,

moreover, that signaling functions other than or in addition to those just named may likewise be governed by the same relay.

When applied to coded signaling systems of the conventional character just considered, the improved approach control apparatus herein disclosed renders the relay AR at each signal location responsive to the approach of a train energize the approach relay AR in step with them.

In the form shown at location D, Fig. l, the referred to entrance end facilities comprise a battery or other source of auxiliary energy AB, an impulse relay IR for transferring the connection of the track rails I and 2 from the track relay TR to battery AB during each off period of the received signal control code, and means including a transformer winding 8 for supplying the relay IR with a pulse of pick-up energy at the be inning of each of the named off periods.

This relay supply winding 8 may, as shown in Fig. 1, be a part of the usual signaling system decoding transformer DT2 or, as shown in Figs. 2, 3, 5, 6 and 7, it may form a part of a separate relay transformer RT. In either case the transformer (DT or BI) is provided with a primary energizing circuit which is controlled by a contact l2 of the code following track relay TR and which derives energy from a direct current source designated by the terminals plus and minus. Each time that the track relay releases the pole changing action of this contact l2 causes to be induced in the secondary winding 8 a pulse of transformer voltage having the polarity designated by the small arrow and which for convenience will be referred to as normal. Each time, however, that the track relay picks up the reverse action of the contact l2 causes to be induced in this winding 8 a pulse of transformer voltage of the opposite or reversed polarity.

Both half waves of voltage from winding 8 are impressed upon the operating winding of the impulse relay IR. This relay, however, is of the polar type and contact l3 thereof occupies the released position (shown in full lines) as long as the relay remains deenergized or receives current of the reversed polarity just described. In that position the contact connects the operating winding of the track relay directly across the track circuit rails I and 2.

When, however, relay IR receives from winding 8 the beforementioned pulse of normal polarity energy, it picks up contact l3 and thereby disconnects relay TR from the track rails and connects the auxiliary battery AB thereacross. In this manner each release of the track relay TR causes the impulse relay IR momentarily to transfer the track rail connection from the winding of track relay TR to the output circuit of battery AB. At the same time, each pick-up of the track relay is ineffective for interfering with the normal connection of the rails with the winding of that relay.

In the form shown at location E. in Fig. 1, my improved exit end facilities comprise a detector relay KR which responds to pulses of auxiliary energy received over the rails I and 2 from battery AB, a circuit controlled by a contact l of that relay for energizing the approach relay AR from a local source designated by the terminals plus and minus, and means for making the relay AR sufiiciently slow releasing to bridge the intervals between recurrent responses of the detector relay.

This detector relay KR is of the code following type and the operating winding thereof is connected in energy receiving relation with the track rails l and 2 only during the off periods of the signal control code which contact 5 of device CR produces. The here represented arrangement of devices CR, KR and AR is similar to that disclosed and claimed in a copending application Serial No. 221,317, filed July 26, 1938, by Edward U. Thomas and now identified as Patent No. 2,172,893 dated September 12, 1939; in this arrangement the first named connection is completed by the coding contact 5 when in its uppermost or 01f period position.

The slow release approach relay AR may be energized in step with the responses of the detector relay KR in any suitable manner. As shown, the contact l5 of the detector relay is directly included in a local direct current energizing circuit for the operating winding of the approach relay. For delaying the release of this relay AR and thereby enabling it to remain continuously picked up as long as its winding reoeives code step pulses of the named energy, use may, of course, be made of any suitable means such as a snubbing impedance (not shown) or internal design expedients' incorporated in the relay. Because of their well-known character, all of the drawing views except Fig. 4 make no attempt to represent any such means.

The function of the exit end tuned alternator TA which is shown at location E in Fig 1 is to generate locally from a direct current source the alternating current energy which at times is required for cab signal control. In the form represented this alternator includes a transformer l! which receives primary energizing current from the direct current terminals plus and minus through a circuit which is periodically pole changed by a reed type of vibrating member l8.

This member may be of iron or other magnetic material and is designed to have a natural rate of vibration which-corresponds to the 100 cycle per second or other desired frequency of the output voltage of the alternator TA. Driving movement is imparted thereto by an electromagnet I!) having an energizing circuit which is completed at point 2!] each time that the reed occupies its lowermost position. In this manner the armature is caused to vibrate at its natural rate as long as the driving circuit therefor is connected with a source of energy.

When in its lowermost position the armature sets up a circuit through which current from the referred to direct current source flows in one direction through the right portion of the primary winding of the transformer ll and when in its uppermost position the reed completes a similar circuit through which current flows in the opposite direction through the left portion of the transformer winding and to the negative supply terminal by way of a mid tap 23, Each complete vibration of the armature l8 thus causes a cycle of alternating current voltage to be induced in the secondary winding of the transformer l1.

'In this manner an electromotive force of the cycle; or other cab signal controlfrequency is generated whenever the approach relay AR releases its contact H and thereby connects the alternator supply conductor 24 with the plus" terminal of the local direct current source. Con-' veniently, this source may take the form of the same local battery (not shown) which supplies lighting current to the signal lamps.

It will be seen, therefore, that in a system of the improved character which is shown in Fig. 1, no line wires whatever are required between signal locations. The control of the wayside signals S is eifected throughthe medium of coded signal control energy transmitted through the track rails l' and 2 in conventional manner the control of the approach relays AR issimilarly effected through the medium of off period pulses of auxiliary energy from battery AB fed forwardly to the section exit; and the supply of the alternating current coded energy for cab signal control is provided through the tuned alternator TA from the track battery TB or other local source of direct current energy.

In operation of the non line wire approach control facilities which are represented in Fig. 1, the track rails l and 2 of section D-E act in the usual manner to transmit energy from one end of the section to the other as long as the section remains unoccupied. Each time, under such conditions, that contact 5 of the coding device CR'is in the lowermost or on code period position the'track battery TB picks up the track relay TR over a circuit which may be traced from the positive terminal of the battery through secondary winding of transformer ll, conductor 26, a current limiting impedance 2?, back contact 5 of device CR, conductor 28, track rail l, c onductor29, the winding ofthe track relay TR, conductor 3|, back contact l3 of relay IR, con doctor 32, the track rail 2, and conductor 33 back to the negative terminal of battery 'IB.

Each timethat the coding contact 5 occupies the uppermost or off code period position and bridges the winding of the detector relay KR across the track rails, the track relay TR at the entrance end of the'section releases and transfersthe primary energizing circuit for trans former DT2 from conductor 35 and the upper half of the transformer primary to conductor 36 and the lower half of the primary. This reversal of excit'ation" induces in the secondary winding 8 of the transformer a pulse of normal polarity voltage which is impressed on the winding of the impulse relay. IR over a circuit extending from the lower terminal of winding 8 through conductor 37, the winding of relay IR and conductor 38 back to'the upper terminal of the transformer secondary. V v

In respondingfcontact l3 of relay IR picks up at the beginning of each of the off periods of the signal control code ancl'disconnects the winding of relay TR from the track rails and connects the auxiliary battery AB thereacross. Under this condition the battery AB picks up the detector relay "KR at the exit end of the section over a circuit which may be traced from the positive terminal of the battery through a current limiting impedance 49, front contact I3 of relay IR, conductor 32, track rail 2, conductor 33, the winding of relay KR, conductor 4|, front contact 5 of device CR, conductor 28, track rail l, and conductors 29 and 42 back to the negative terminal of battery AB.'

Under the influence of each of these auxiliary pulses of energy received from the trackway', contact l5 of code following detector relay KR picks up and completes for the approach relay AR a local energizing circuit which may be traced from the positive terminal of a suitable supply source through front contact 15, conductor 43 and the Winding of relay AR back to the negative terminal of the supply source.

As a result of these recurring pulses of local energization, the slow release approach relay AR now holds contacts 9 and H1 continuously picked up, thereby maintaining the wayside signal Se and the tuned reed alternator TA at location E deenergized as long as the track section DE remains vacant.

In the event that a train comes into the track section DE, the usual shunting action of its wheels and axles reduces to a very low value the potential difference between the rails l and 2 and thus deprives both of the relays TR and KR of pick-up energy. Relay KR now remains released continuously and the supply of local energization to the approach relay AR is discontinued. In consequence, contacts 9 and I l of that relay now complete energizing circuits for signal Se and the tuned reed alternator TA.

As a result the named wayside signal now lights the particular lamp selected by the decoding equipment l and the tuned reed alternator TA supplies the rails of track section D-E with a pulse of alternating current energy each time that the contact of device CR occupies its lowermost position. As has been mentioned this energy is suitable for the control of train carried cab signals and the circuit over which it is supplied may be traced from the right terminal of the secondary winding of transformer I! through conductor 26, impedance 21, back contact 5 of device TR, conductor 28, track rail I, the wheels and axles (not shown) of the train, rail 2, conductor 33, and track battery TB back to the left terminal of the transformer secondary.

As soon as the rear of the departing train clears the exit of section DE the coded energy from track battery TB is again transmitted by the rails to the track relay TR at the section;

entrance. That relay once more responds and the operation of contact I! thereof causes the impulse relay IR again to connect the track rails in energy receiving relation with the auxiliary battery AB during each of the off code periods.

These auxiliary energy pulses are, in turn, trans mitted by the rails to the detector relay KR at the exit location E.

In responding to them that relay again causes the approach relay AR to receive recurrent pulses from which it receives pick-up energy are so designed that the relay will pick up contact l3 relatively soon after the beginning of each off period of the received signal control code and will maintain this contact picked up until just before the beginning of the on period for the particular code wherein the periods are shortest. In the case of the three indication signaling system referred to in an earlier portion of this specification, this limitation in the length of pickup time for the contact l3 will, of course, be

determined by the highest speed or 180 energy pulse per minute code. Such a code has a cycle length of /1 second and an off period length of about %00 second.

With this 180 energy pulse per minute code, it is found possible to maintain the impulse relay contact l3 picked up for a total of approximately V second during each of the off periods. This allows a margin of approximately second from the time that the track relay TR first starts to release until the impulse relay IR fully picks up and a period of approximately the same length from the time that the impulse relay IR starts to release until the track relay picks up at the beginning of the next on code period. Such a relation assures about the maximum practical time of connection of the auxiliary battery AB with the track rails during each off period of the code without producing overlapping or delay in the reconnection of the winding of the track relay TR with the rails until after the beginning of the succeeding on period.

As has been pointed out, the impulse relay IR is preferably of a polarized design and may satisfactorily be of a normally quick acting type in both the pick-up and the drop-out directions. Even though the pulse of normal polarity energy supplied through transformer winding 8 at the beginning of the off period may be much shorter than the second total time of relay pickup, the desired delay in release is provided through the snubbing action of the winding 8 which, through conductors 31 and 38, is directly bridged across the terminal of the relay winding.

Once selected to meet the limiting conditions of the highest speed code of the signaling system, the relay IR provides the same fixed period of rail connection transfer for all other codes.

That is, even with the lower speed or '75 pulse per minute cod'e previously referred to, the period of rail connection transfer will still be approximately 7 second even though the total length of the 75 code off period is of the much extended order of 7100 second.

In all cases, however, my entrance end facilities afford an improved means for introducing the pulses of auxiliary energy into the track circuit without interfering with the normal code following operation of the signaling system track relay TR. From a standpoint of energy conservation, these facilities are of special advantage since the maintain the auxiliary energy supply circuit completely disconnected from the track rails during the on code periods, and thereby enable the track relay TR to receive the full value of trackway energy available at its point of connection with the rails. Moreover, during each of the off code periods, the facilities maintain the track relay TR completely disconnected from the rails and thus allow all of the auxiliary energy from battery AB to be impressed upon the track circuit for the purpose of transmission forwardly to the operating winding of the code following detector relay KR at the section exit.

Considering further my improved exit end facilities which include this detector relay KR and of which the tuned reed alternator TA also forms a part in the arrangement of Fig. 1, the secondary winding of the alternator transformer I1 is designed with a sufficiently low resistance as not to interfere objectionably with the transmission of direct current from the battery TB to the rails l and 2. The winding of the detector relay KR, moreover, is connected with the rails only during the off code period produced by device CR and ing across the rails.

in this way it is prevented from diverting from the trackway the coded signal control energy from either or both of the sources TB and TA.

Similarly, since these sources are disconnected from the rails during each off period of the code which device CR produces, the circuits thereof do not divert from the operating winding of relay KR the auxiliary energy received over the rails l and 2 from the battery AB. In this manner maximum utilization of the different forms of energy for the particular purposes intended is at all times assured.

Preferably, the resistance of the winding of the detector relay KR is kept relatively low in order that the undesirable effects of track storage of the signal control energy from the track battery TB may be counteracted during the off code periods when contact connects that wind- As is known, such energy tends to accumulate in the rails and ballast of each of the signaling system track circuits as a result of the repeated application thereto of the direct current code pulses from the track battery or other direct current source at each section exit. Unless counteracted, the potential appearing between the rails l and 2 because of this storage effect may, over a period of time, build up to a value which becomes sufi'icient even to prevent the signaling system track relay TR at the section entrance from releasing during the off periods of the signal control code.

The counteraction of track storage energy which is referred to above results from the low resistance rail discharge path which the winding of relay KR provides during each of the off code periods when contact 5 of device CR connects-it across the rails I and 2. This shunting action assures that the rail potential will be suificiently reduced at the beginning of each off period to enable the entrance end track relay to drop out promptly in the desired manner.

If desired the basic counteracting provision just described may be supplemented by poling the auxiliary battery AB oppositely to the track battery TB. Such an arrangement is shown in 3.. Fig. 1 wherein the exit end track battery TB makes rail l positive with respect to rail 2 each time it is connected to the rails over coding contact 5, while the entrance end auxiliary battery AB makes rail 2 positive with respect to rail i' each time that it is connected to the track circuit by transfer contact I3 of the impulse relay IR. Hence, the off period pulses of auxiliary energy provide a direct counteracting influence which further reduces the potential of track battery polarity which remains between the track rails following each disconnection of the battery TB therefrom.

Referring to Fig. 2, I have there represented cut section facilities which are suitable for use with the approach control scheme of Fig. 1. These facilities are required when, because of excessive length or for any other reason, it becomes necessary to sub-divide the main signal block length of track into two or more track circuits. In Fig. 2 one location of such a subdivision is designated by the character Da and to facilitate explanation it will be assumed that this particular location is constituted by interposing insulated rail joints 3 between the limits D and E of the signal block of Fig. 1.

The facilities of Fig. 2 are arranged to perform three functions. First they repeat the coded direct current signal control energy received from the forward section rails around the joints 3 and of transformer 11 into the rails of the section to the rear of location Da. Aiding in this first function is a code following track relay TR which is operated by energy received from the forward section rails, a track battery TB which serves as an energizing source for the rails of the rear section, and a coding contact 5 operated by the relay TR and arranged to complete the rail supply circuit for the rear section each time that the track relay TR releases and to interrupt it each time that the relay is picked up.

This arrangement of Fig. 2 employs what will be termed as back contact codingfrom the fact that each off period of the forward section code produces an on period in the rear section code while each on period of the forward code is accompanied by an off period in the rear code. As in the corresponding facilities of Fig. 1, the referred to rail supply circuit of Fig. 2 may be traced from the positive terminal of battery TB through the secondary winding of the tuned reed alternator TA, conductor 26, impedance 27, back contact 5 of device TR, conductor 28, track rails l and 2 and conductor 33 back to the negative terminal of battery TB. I

The second function performed by the cut section facilities of Fig. 2 is to introduce the off code period pulses of auxiliary energy into the rails of the track section ahead of location Da. Participating in this second function is an auxiliary battery AB, an impulse relay IR which (as in Fig. 1) transfers the rail connection from the winding of the track relay TR to battery AB, and a transformer RT which supplies relay IR with a pulse of pick-up energy at the beginning of each off code period.

Each time that the track relay TR releases, contact l2 thereof interrupts the direct current exciting circuit for transformer RT and causes winding 8 thereof to supply relay IR with a pulse of normal polarity pick-up energy. Contact l3 now transfers the normal connection of the rails l and 2 from the operating winding of relay TR to the terminals of the auxiliary battery AB and thus supplies the auxiliary energy to the trackway in the manner named.

The third function performed by the cut section facilities of Fig. 2 is to supply the rails of the track section to the rear of location Da with coded alternating current energy suitable for cab signal control whenever a train enters that rear section. Aiding in this third function is a tuned reedalternator TA, a slow release approach relay AR for connecting this alternator with a direct current supply source over contact I I, and a code following detector relay KR for energizing (over contact l5) the approach relay in step with the pulses of auxiliary or off code period energy which are received from the rear section rails.

Aslong as these pulses continue to be received relay AR is periodically energized, as in the system of Fig. 1, and holds contact ll picked up to maintain the alternator TA inactive. When, however, a train comes into the rear section, relay KR continuously releases, relay AR becomes deenergized continuously and the alternator then [is connected with the direct current operating source over conductor 24 and relay contact ll. Each time, now, that coding contact 5 of relay TR occupies the lowermost position the transformer ll of the apparatus TA impresses cycle or other cab signal control frequency energy upon the rear section rails l and 2 by way of the circuit previously traced as including conductors 28 and 33.

It will thus be seen that the cut section facilities of Fig. 2 may be interposed within the limits of a signal block length of track, such as shown at D-E in Fig. 1, without interfering with the operation either of the main signaling scheme or of the approach control facilities of my invention which are used therewith. If desired (not shown in Fig. 2) the relative polarity of the two track circuits which adjoin at location Da may be staggered for the purpose of providing the usual protection against broken down rail joints.

Referring now to Fig, 3, I have there represented an extended form of exit end facilities which may be substituted for the previously described exit end apparatus which is represented at location E in Fig. 1. As in Fig. 1, the apparatus of Fig. 3 employs coding, detecting and approach relay devices CR, KR and AR. It differs, however, in that the continuously operating coding device CR2 is provided not only with the main coding contact 5 but also with a second contact 50. Likewise, the detector relay designated as KRZ in Fig. 3 has not only the Fig. 1 pick-up winding 5| which contact 5 bridges across the track rails during the off periods of the signal control code, but also a second or stick winding 52 arranged in the manner disclosed and claimed by the before referred to copending application Serial No. 221,317 of Edward U. Thomas (filed July 26, 1938),

The purpose of this added or stick winding is to make possible a reduction in the period of delay of the approach relay AR in releasing its contacts 9 and ii following each prolonged interruption of its energizing circuit at contact [5 of the detector relay KRZ. As is more completely described in the copending Thomas application just mentioned, use of a detector relay having such a stick winding quickens the response of the approach control relay AR to the entry of a train into the-associated track section and thus avoids objectionable flips in the cab signals of a train when that train first passes over the insulated rail joints 3 at the section entrance.

As shown in Fig. 3, the track battery TB is used as the source of energization for the operating winding of the approach relay AR. Moreover, the facilities for supplying the rails with coded alternating current energy for cab signal control are modified to the extent that the tuned alternator represented at TA in each of Figs, 1 and 2 is replaced by a track transformer TT having a secondary winding which is serially included in the rail supply circuit of which battery TB forms a part. At proper times the primary winding of this transformer is energized over a conductor 53 from a suitable alternating current source designated by the terminals B and C.

With such an arrangement, of course, it is imperative that an alternating current transmission line be provided along the right-of-way for the purpose of distributing the alternating current energy to each of the signal locations of which E of Fig. 3 is representative. As already pointed out, the use of the tuned alternator TA as in Fig, l eliminates the need for such a line and allows all of the signal control and approach governing functions to be carried out without line wires of any kind and by the aid of energy derived from the locally installed track and auxiliary batteries TB and AB.

For lowering the impedance which the secondary winding of transformer TT introduces into the rail supply circuit under inactive transformer conditions, the contact ll of the approach relay AR preferably is arranged (as shown in Figs. 3, 4, 5 and 6) to short circuit the primary winding of the transformer whenever the approach relay is picked up. Thus, whenever the track section to'the rear of the location is vacant, this primary shunting path is completed from the lower terminal of the primary of transformer TT through conductor 55, front contact H of the relay AR, and the conductor 63 back to the upper terminal of the transformer primary.

In operation of the extended exit end facilities of Fig. 3, both of the contacts 5 and 50 of the coding device CR2 function in parallel in making and breaking the circuit through which the track rails and 2 receive energy from the track battery TB, and also from the track transformer TT under certain conditions. Each time that the contacts occupy the lowermost position (shown in full lines), the rails are connected with the battery TB over a circuit which may be traced from the positive supply terminal of that battery through conductor 56, contacts 5 and 50 in parallel, conductors 59 and 28, the track rails and 2,

conductor 33, impedance 2?, the secondary of transformer TT and conductor 51 back to the negative terminal of the track battery.

Each time that the contacts 5 and 50 occupy the uppermost or off code period position, contact 5 connects the pick-up winding 5| of the detector relay KRZ with the track rails and thus conditions it for receiving auxiliary energy therefrom over a circuit which extends from rail 2 through conductors 33 and 58, the relay winding 5|. conductor 4|, front contact 5 of device CR2 and the conductors 59 and 28 back to the track rail This auxiliary energy, when received, comes from the approach battery AB of entrance end facilities of the character which are represented at location D in Fig. 1. In considering the operation of Fig. 3, it will be helpful to assume that the rails and 2 extending rearwardly from location E thereof terminate in facilities of the character represented at D in Fig. 1.

In the off code position the second contact 55 of the coding device CR2 completes for the stick winding 52 of the detector relay KR2 a stick circuit which was set up by a contact 6| of the detector relay when that relay became picked up by the pulse of auxiliary energy which circulated through the pick-up winding 5|. This stick circuit functions to continue the pick-up of relay KR2 for the full duration of the off code period and it may be traced from the positive terminal of the track battery TB through conductor 56, front contact 50 of device CR2, conductor 62', front contact 6| of relay KRZ, the winding 52 of that relay, and conductors 53 and 51 back to the negative terminal of battery TB.

In this manner each pulse of auxiliary energy received from the rear during an off code period picks up the detector relay KB? and causes that relay to remain picked up until contact 55 of coding device CR2 is returned to the lowermost position at the beginning of the succeeding on code period. As long as the track section to the rear of location E remains vacant, therefore, relay KR2 responds in this manner during each off period and causes contact |5 thereof periodically to complete for the slow release approach relay AR an energizing circuit which may be traced from the positive terminal of battery TB through conductor 56, front contact l5, the wind- "2,275,838 'ing of relay AR and conductors 6-3 and 'lback to the negative terminal of the track battery.

Because of its slow release characteristics the approach relay AR now holds its contacts 9 and I I picked up continuously and thus maintains the wayside signal Se and the track transformer TT at location E in their normally inactive condition.

Upon the entry of a train into the section to the rear of Fig. 3 location E, the supply of the auxiliary energy to the detector relay KR2 is cut off due to the usual shunting action of the train wheels and axles. The detector relay now remains released continuously, relay AR is deenergized continuously, and it releases contacts 9 and l I, thereby completing the lighting circuit for the wayside signal Se and connecting the primary winding of the track transformer TT with the alternating current source B -C.

Each time, now, that the contacts of coding device CR2 are in the lowermost or on code position the secondary winding of this transformer supplies the track rails with a pulse of alternating current energy by way of a circuit which may be traced from the lower terminal of the transformer secondary through conductor 51, the track battery TB, conductor 55, contacts 5 and 50 of device CR2 in parallel, conductors 59 and 28, track rail l, the wheels and axles (not shown) of the train, rail 2, conductor 33 and impedance 2'! back to the upper terminal of the transformer secondary.

As soon as the rear of the departing train clears the exit end location E, the supply of off period pulses of auxiliary energy to the pick'up winding 5| of the detector relay KRZ is resumed, this relay responds and recurrently completes at contact IS the energizing circuit for the slow release approach relay AR, and that relay once more picks up thereby interrupting at contact 9 the lighting circuit for the wayside signal Se and disconnecting at contact l the track transformer T1 from the alternating current source BC.

Referring to Fig. 4, I have there represented a single signal location Q of a coded track circuit signaling system which employs decoding apparatus of one representative form and with which the earlier described approach control facilities of my invention are combined. As in the equipments of the earlier figures, this signaling system is of the three indication type and it employs two different signal control codes produced by devices CT! and GT2 and respectively consisting of 75 and 180 energy pulses per minute.

The decoding equipment of Fig. 4 includes first and second decoding relays DR and DRISil which respectively respond to both of the 180 and the '75 pulse per minute trackway codes and to the 180 code only. Decoding relay DRlBil is connected to receive energy through a resonant or frequency selective unit DUMB and from a transformer DT. This transformer is excited from any suitable direct current source over a pole changing contact of the code following track relay TR and by way of a circuit which includes a conductor 85 and a front contact 13 of the first decoding relay DR15.

When arranged in the manner shown, this contact 73 disconnects the transformer DT from its supply source whenever the track relay TR fails to respond to a trackway code, as when the track section ahead of location Q is occupied by a train. The same contact, moreover, renders The companion decoding relayDRlB of Fig. 4 is controlled by a contact lfi of thetrack relay TR, which contact acts in cooperation with an associated repeater relay FP. Both of the devices DR'Hi and FP are slow releasing. As long as thetrack relay follows a code of the 75 pulse per minute or higher rate, recurrent pulses of energizing current from a local direct current source are supplied to both of the named relays. In the case of relay FP the circuit is completed by contact 46 when picked up and in the case of relay DRl5 the circuit is completed only when the code transmitter CT! inactive at all times that the named forward section is vacant.

contact 36 is released.

This latter circuit includes a front contact 81 of the repeater relay FP arranged to insure that a continuously maintained condition of the track relay TR, either released or picked up, can never cause decoding relay DRIE to respond. When, however, the track relay operates contact 46 in code following manner, the slow release repeater relay FP holds contact Bl picked up and thereby enables ea'ch release of contact 4% to complete the energizing circuit for the decodingv relay just named. In this manner, the relay DR15 picks up only when the track relay TR responds to coded energy of the '75 pulse per minute or higher rate.

The two decoding relays DR75 and DRI of Fig. 4 are provided with contacts 66 and '6! which control the wayside signal S at the same location. Moreover, relay DR15 is provided with a contact 69 which selects which of the two code transmitters CTI and GT2 is to control the energizing circuit for the associated coding relay CR2. This relay may or may not be provided with the snubbing facilities.

In the equipment of Fig. 4 a track transformer TT and a continuously available supply B--C of alternating current energy are employedfor providing the cabsignal control code. In the form represented these particular facilities are a duplicate of those of corresponding designations which are represented in Fig. 3 and for this reason further description is not required.

In operation of the equipment shown in Fig. 4, the signaling system portions thereof function in conventional manner while the approach control portions thereof operate in a way which is comparable to that already explained in the earlier figures of the drawings. Hence, it will sufiice to point out that as long as the protected stretch of track l-2 remains vacant the exit end facilities for each section supply the rails thereof with energy of the coding, the entrance end track relay TR for each section responds to this energy, the associated decoding relays DR75 and DRlsll at each signal location are both picked up, the clear lamp G of the controlled wayside signal S has its lighting circuit set up, and contact liiil of device GT2 is included in the energizing circuit of the coding relay CR2 for the track section to the rear.

Each release of each section track relay TR now causes the impulse relay IR to pick up and momentarily connect the auxiliary battery AB with the section rails. At the exit end of the section, these auxiliary energy pulses pick up the detector relay KR2 in step therewith, it recurrently completes the energizing circuit for the slow release approach relay AR and that relay, in turn, maintains the wayside signal '3 dark and keeps the track transformer TT disconnected from its supply source B-C.

In the event that a train approaches the signal location Q of Fig. 4, the shunting action of its wheels and axles deprives the detector relay KRZ of the pick-up pulses of auxiliary energy and allows it to release its contacts continuously. Now continuously deenergized, relay AR releases and contact 9 completes the before set up lighting circuit for the lamp G of the wayside signal Sq. At the same time contact ll of relay AR connects the primary of the track transformer TT with the alternating current source BC and causes the secondary of that transformer to introduce into the rail supply circuit a cab signal control voltage of the 100 cycle per second (or other preselected) frequency.

Each time noW that the contacts 5 and 50 of the coding device CR2 are in the lowermost position this transformer T1 supplies the rails with alternating current energy over a circuit which extends from the lower terminal of the transformer secondary, through conductor 51, the track battery TB, conductor 58, coding contacts 5 and 5B in parallel, conductors 59 and 28, track rail 1, the train wheels and axles (not shown), track rail 2, conductor 33, and impedance 21 back to the upper terminal of the transformer secondary. This alternating current energy is superimposed upon the direct current signal control energy from track battery TB which under all conditions reaches the rails each time that the coding device contacts 5 and 511 are in their lowermost position.

The two approach controlled signaling functions above discussed continue active until the rear of the departing train clears the location Q. When that happens the rails l and 2 once more transmit auxiliary energy to the pick-up winding 5| f the detector relay KR2, that relay restores the recurrent energization to the approach relay AR and it, in turn, picks up contacts 9 and H to return the wayside signal Sq and the track transformer TT to their normally inactive condition.

In the event that a second train approaches location Q from the rear before the first train has moved out of the track section ahead of this location, the cycle of operations just described will be repeated with the following differences: (1) Instead of operating on the 180 pulse per minute rate the coding device CR2 will be operating on the 75 pulse per minute rate; and (2) until the rear of the forward train clears the exit end of the section of which location Q marks the entrance, the approach relay AR will remain deenergized (at contact 12 of decoding relay DR'I5) even though the detector relay KRZ responds in normal manner to the return pulses of auxiliary energy which are received from the rear section rails. As soon, however, as the advance train does clear the forward section, the decoding relay DRT picks up contact 12 and relay AR then becomes subject solely to the control of the contact I5 of the detector relay KR2.

It will further be noted that in the representation of Fig. 4 the polarities of the forward and the rear track sections are staggered, This staggering is for the purpose of providing the usual protection against broken down rail joints. As has already been pointed out, however, the improved approach control facilities herein disclosed are operable with signaling systems which both do and do not employ staggered polarities of adjacent track circuits.

Referring to Fig. 5, I have there represented cut section facilities which are suitable for use with the approach control apparatus of the earlier described figures. Typically, as already explained, such facilities will be used when the main signal block length of track is, because of excessive length or for other reasons, divided into two track circuit sections. In Fig. 5 the junction of one point of such division is indicated at Qa.

As in the case of the corresponding cut section facilities of Fig. 2, those represented in Fig. 5 perform three functions. First they repeat around the insulated joints 3 and into the rails of the section to the rear of the cut the coded track circuit energy which is received from the rails of the forward section. Effecting this first function is a code following track relay TRZ which is operated by energy received from the forward rails, a track battery TB which serves as an energizing source for the rails of the rear section, and a coding contact 5 which completes the rear section supply circuit each time that the relay TRZ is picked up.

This coding contact 5 and a companion contact 5B correspond to the similarly identified members of each of Figs. 3 and 4 and they differ therefrom in that they form a part of relay TR2 rather than of relay CR2 and in that the rail supply circuit is completed when the contacts'are in the uppermost rather than the lowermost position. In that event battery TB supplies the rails with current over a circuit which extends from the positive terminal of the battery through conductor 56, front contact 5 of device CR2, conductor 28, track rail 2, rail I, conductor 33, impedance 21, the secondary winding of the track transformer TT, and conductor 5! back to the negative terminal of the battery TB. In this manner each on" period of signal control code received from the forward section is repeated as an on period into the rails of the rear section and each off period of the forward code is accompanied by an off period of the rear section code. This arrangement will be referred to as front contact coding.

The second function performed by the cut section facilities of Fig. 5 is to supply the forward section rails with a pulse of auxiliary energy during each off period of the code to which relay TRZ, responds. Participating in this second function is a source of auxiliary energy AB, an impulse relay IR which transfers the track circuit connection from the operating winding of relay PR2 to battery AB, and a transformer RT which supplies relay IR with pick-up energy each time that contact l2 of relay TR2 releases. These devices cooperate in the manner already explained in connection with Fig. 2 to perform the second function named.

The third function performed by the cut section facilities of Fig. 5 is to supply the rails of the rear section with coded alternating current energy suitable for cab signal control whenever a train enters that rear section. Aiding in this third function is a track transformer TT, a supply circuit therefor including terminals B and C and controlled by contact H of a slow release approach relayAR, and means including a contact l5 of a detector relay KR2 for energizing relay AR in step with the pulses of auxiliary energy which are received from the rear section rails.

As long as these pulses continue to be received relay AR is periodically energized in the manner already explained in connection with Figs. 3 and 4, and contact ll thereof then remains picked up to maintain transformer .TT inactive. When, however, a train comes into the rear section, relay KR continuously releases, relay AR iscontinuously deenergized, and contact H thereof now releases to connect transformer T1 with the alternating current source B-C and thus cause coding contact of device 'I'RZ to impress the output of transformer TT upon the rear section rails each time that the contact is in its uppermost position.

When in its lowermost position this same contact connects the pick-up winding 5| of the detector relay 'KRZ in energy receiving relation with the track rails. Likewise, when the second contact 56 of device CR2 is in the lowermost position it sets up for the stick winding 52 of the relay KRZ an energizing circuit which is completed when contact iii of the same relay becomes picked up. Since the manner in which this detector relay K-RE responds is no different than that in the earlier described figures, no further description need be given here.

It will be seen that the cut section facilities of Fig. 5 may be interposed within the limits of a signal block length of track without interfering with the operation either of the main signaling scheme or of the improved approach control system of my inyention which is used therewith. As shown in Fig. 5, the relative polarities of the two there adjoining track circuits are staggered for the purpose of providing the usual protection against broken down rail joints.

Referring to Fig. 6, I have there represented cut section facilities which are a duplicate of those shown in Fig. 5 with the exception that they are modified to provide back contact coding instead of the front contact coding. Here the supply circuitfo-r the rear section rails is completed when the contacts 5 and 5% of device CR2 are in the released position and the circuit is interrupted when the contacts are picked up. This means that each on period of the forward section code produces an 1011* period in the rear section code and that each off period of the forward section code is accompanied by an on period in the rear section code.

The advantage of this back contact coding? is that it compensates for distortion of the track circuit code which accompanies its transmission along the length of. the track circuit. The tendency of this distortion is to lengthen the off periods and shorten the on periods and by repeating the coded energy around the insulated joints 3 (see Fig, 5) over the back contact of the track relay TF2 in the manner shown in Fig. 6, the abnormally long off periods are not amplified but instead are converted into correspondingly longer on periods in the rear section. By the time these have been transmitted to the exit end of the rear section the distorting influence before referred to has a tendency to reduce them to the desired condition of equality.

From the foregoing it will be seen that I have made important improvements in that scheme of approach control without line wires wherein the rails of each unoccupied signal block length of track transmit code step pulses of auxiliary en- .ergy forwardly from the block entrance to effect the energization of a slow release approach relay at the block exit.

In particular, I have made provision for supplying the referred to pulses of auxiliary energy to the entrance end of each track circuit in an with a wide variety of different improved manner whichdoes not interfere with the normal code following operation of the associated signaling system track relay and which eliminates all wastage of power at the location of that relay; I have also made provision for receiving these pulses at the exit end of the signal block and for energizing the slow release approach'relay in step with them in an improved manner which quickens the response of that relay to the entry of a train into the signal block; I have additionally provided for a double functioning of the contacts of the track circuit coding devices in their control of the combined signaling and approach governing equipment which is installed at the exit end of each signal block; and still further, I have provided cut section facilities which are suitable for use with approach control means of the improved type herein disclosed.

As all of these improvements are entirely a function of .the track circuit and apparatus which is directly associated therewith, theyare independent .of the coding and decoding facilities of the coding signaling system and hence are usable types and forms of such facilities.

While I have explained my invention in an application wherein both the lamps of the wayside signal and the supply of alternating current cab signal energy are approach controlled, it will be understood that either one of these functions may be performed separately and that other comparable functions may also be provided for in my new system.

Although I have herein shown and described only a few forms of approach control apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination, a section of railway track, a source of control energy for said section, a code following detector relay having a pick-up circuit and a stick circuit, a coding device having contacts which shift from a front to a back position and from said back to said front position repeatedly and in synchronous relation with respect to each other, a first contact of said device which in a given one of said two positions connects the section rails to said source and thereby causes those rails to receive an on period pulse of control code energy and which in the other of said positions transfers said rail connection to said detector relay pick-up circuit and thereby produces a control code off period, means responsive to the said on period pulses of control code energy which said section rails transmit for further supplying those rails with auxiliary energy in the form of pulses that recur in step with said control code off periods and that pick up said detector relay during each of those off periods, a second contact of said device which in said given or on period position parallels said first contact in completing said rail-to-source connection and which in said other or off period position completes said detector relay stick circuit from the time that said detector relay picks up until the end of the said off code period within which the pick-up occurs, and traffic governing apparatus controlled r by said detector relay and selectively responsive according as that relay is recurrently picking up and releasing or is continuously released.

2. In combination, a section of railway track, a source of control energy for said section, a. code following detector relay having a pick-up circuit and a stick circuit, a coding device having contacts which shift from a front to a back position and from said back to said front position repeatedly and in synchronous relation with respect to each other, a first contact of said device which in a given one of said two positions connects the section rails to said source and thereby causes those rails to receive an on period pulse of control code energy and which in the other of said positions transfers said rail connection to said detector relay pick-up circuit and thereby produces a control code off period, means responsive to the said on period pulses of control code energy which said section rails transmit for further supplying those rails with auxiliary energy in the form of pulses that recur in step with said control code off periods and that pick up said detector relay during each of those off periods, a second contact of said device which in said given or on period position parallels said first contact in completing said rail-to-source connection and which in said other or off period position completes said detector relay stick circuit from the time that said detector relay picks up until the end of the said 01f code period within which the pick-up occurs, a slow release approach relay controlled by said detector relay and maintained picked up as long as that relay continues to receive said recurring pulses of auxiliary pick-up energy, and traffic governing apparatus controlled by said approach relay and selectively responsive according as that relay is picked up or released.

3. In combination with a section of railway track, approach control facilities therefor comprising (l) at the section exit: a source of control energy, a code following detector relay having a pick-up circuit and a stick circuit, a coding device having contacts which shift from a front to a back position and from said back to said front position repeatedly and in synchronous relation with respect to each other, a first contact of said device which in a given one of said two positions connects the section rails to said source and thereby causes those rails to receive an on period pulse of control code energy and which in the other of said positions transfers said rail connection to said relay pick-up circuit and thereby produces a control code off period,

a second contact of said device which in said given or on period position parallels said first contact in completing said rail-to-source connection and which in said other or off period position sets up said detector relay stick circuit for the full off period continuance, and traffic. governing apparatus controlled by said detector relay and rendered active only when said relay remains continuously released; and (2) at the section entrance: means responsive to the recur- I ring on period pulses of said control code energy which are there received for further supplying said rails with auxiliary energy in the form of pulses that recur in step with said control code off periods and that cause said detector relay recurrently to pick up as long as said section remains vacant.

4. In combination, a section of railway track, a source of control energy for said section, a code following detector relay having a pick-up circuit and a stick circuit, a code producing relay which has an operating winding that receives recurring pulses of energizing current and which has contacts that occupy a front position during each of said received pulses and a back position when said winding is deenergized, a first contact of said code producing relay which in a given one of said two positions connects the section rails to said source and thereby supplies those rails with an on period pulse of control code energy and which in the other of said positions transfers said rail connection to said relay pick-up circuit and thereby produces a control code off period, means responsive to the recurring on period pulses of said control code energy which said section rails transmit for further supplying those rails with auxiliary energy in the form of pulses that recur in step with said control code off periods and that pick up said detector relay during each of those off periods, a second contact of said code producing relay which in said given or on period position parallels said first contact in completing said railto-source connection and which in said other or off period position completes said detector relay stick circuit from the time that the detector relay picks up until the end of the said off code period within which the pick-up occurs, and traflic governing apparatus controlled by said detector relay and selectively responsive according as the said pick-up circuit for that relay continues to receive said recurring pulses of auxiliary energy or becomes continuously deenergized due to the entrv of a train into said section.

5. In combination, a control circuit comprising a pair of conductors which normally are capable of transmitting energy between the two circuit ends but which at times are rendered incapable of such transmission, a source of energy for said control circuit, a code following detector relay having a pick-up winding and a stick winding, a coding device having first and second contacts which shift from a front to a back position and from said back to said front position repeatedly and in synchronous relation with respect to each other, means including said first coding contact and effective when that contact is in a given one of said two positions for connecting said circuit conductors to said source whereby to cause those conductors then to receive an on period pulse of control code energy, means also including said first coding contact and effective when that contact is in the other of said two positions for transferring said circuit conductor connection to said relay pick-up winding whereby then to produce a control code off period, means responsive to the said on period pulses of control code energy which said circuit conductors transmit for further supplying those conductors with auxiliary energy in the form of pulses that recur in step with said control code off periods and that pick up said detector relay during each of those off periods, means including said second coding contact and effective when that contact is in said given or on period position for paralleling said first contact in completing said conductor-to-source connection, means also including said second coding contact and effective when that contact is in said other or off period position for completing said detector relay stick circuit from the time that said detector relay picks up until the end of the said off code period within which the pick-up occurs, and apparatus controlled by said detector relay and selectively responsive according as that relay is or is not receiving said recurring pulses of auxiliary energy.

6. In combination, a control circuit comprising a pair of conductors which normally are capable of transmitting energy between the two circuit ends but which at times are rendered incapable of such transmission, a source of energy for said control circuit, a code following detector relay having a pick-up winding and a stick winding, a coding device having contacts which shift from a front to a back position and from said back to said front position repeatedly and in synchronous relation with respect to each other, a first contact of said device which in a given one of said two positions connects said circuit conductors to said source and thereby supplies those conductors with an on period pulse of control code energy and which in the other of said two positions transfers said circuit conductor connection to said detector relay pick-up circuit and therebyv produces a control code ofi period, means responsive to the said on period pulses of control code energy which said circuit conductors transrnit for further supplying those conductors with auxiliary energy in the form of pulses that recur in step with said control code off periods and that pick-up said detector relay during each of those ofi periods, a second contact of said coding device which in said given or on period position parallels said first contact in completing said conductor-to-source connection and which in said other or oil period position completes said detector relay stick circuit from the time that the detector relay picks up until the end of the said off code period within which the pickup occurs, and apparatus controlled by said detector relay and selectively responsive according as that relay is or is not receiving said recurring pulses of auxiliary energy.

HERMAN G. BLOSSER 

